The New 40% First-Year Allowance Does Not Apply to Commercial Solar
Reviewed by the Commercial Solar Finance editorial team (we take no installer or lender commissions). Last reviewed: June 2026.
The Autumn Budget 2025 introduced a new 40% first-year allowance from 1 January 2026, and businesses are asking whether it improves the tax case for solar. The short answer: no — it does not apply to commercial solar PV, because solar is a special-rate asset and the new allowance is main-rate only. Here is exactly why, and what solar claims instead.
Does the 40% FYA apply to solar? No.
The new 40% first-year allowance (from 1 Jan 2026) is for main-rate plant and machinery. Commercial solar PV is special-rate (an integral feature), so it is excluded. Solar instead uses the Annual Investment Allowance — 100% relief to £1m — which remains the best relief available to it.
HMRC classifies solar PV as an integral feature of a building, which places it in the special-rate pool (HMRC CA22335). The 40% first-year allowance is restricted to main-rate expenditure. Because solar is special-rate, it falls outside the new allowance entirely. The same special-rate classification is why the separate main-pool writing-down allowance cut (18% to 14% from April 2026) also does not touch solar — that change applies to the main pool, while solar sits in the 6% special-rate pool.
">What the new 40% first-year allowance actually covers
Announced in the Autumn Budget 2025 and effective from 1 January 2026, the 40% first-year allowance gives 40% first-year relief on qualifying main-rate plant and machinery. It was designed to support investment where other first-year allowances are not available — for example, assets bought for leasing, and unincorporated businesses. Second-hand assets and cars are specifically excluded.
| Feature | The new 40% FYA |
|---|---|
| Effective from | 1 January 2026 |
| Rate | 40% in year one |
| Asset class | Main-rate (main pool) plant & machinery |
| Excludes | Special-rate assets (incl. solar PV), second-hand assets, cars |
| Designed for | Assets that miss other FYAs (e.g. for leasing) and unincorporated businesses |
What commercial solar claims instead — and why it is better anyway
Solar does not need the 40% FYA, because the relief it does qualify for is more generous:
Annual Investment Allowance — 100% to £1m
The AIA gives 100% first-year corporation-tax relief on the full system cost up to £1,000,000 per year, and it applies to special-rate assets. For the vast majority of commercial solar projects (under £1m) this means full relief in year one — better than the 40% the main-rate allowance would have given.
50% special-rate first-year allowance — above the cap
For spend above the £1m AIA limit, solar qualifies for the 50% special-rate first-year allowance, with the residue written down at 6% per year. The 40% main-rate FYA is not an alternative for this excess.
Bottom line: the headline 2026 capital-allowance changes are main-rate measures. For commercial solar, the AIA at 100% remains the dominant relief and is unaffected. See the full picture in our capital allowances on solar panels guide. Figures verified against GOV.UK and the Autumn Budget 2025 measures; general information, not tax advice.
The three 2026 changes and what each means for solar
It helps to see all three Autumn Budget 2025 capital-allowance changes together, because the confusion comes from reading a main-rate headline and assuming it applies to everything. The new 40% first-year allowance (from 1 January 2026) is main-rate only — solar is excluded. The main-pool writing-down allowance cut from 18% to 14% (April 2026) is main-pool only — solar's 6% special-rate pool is untouched. And the Annual Investment Allowance stays at 100% to £1m on special-rate assets — so solar's headline relief is unchanged and remains the most generous it can claim. Two of the three changes simply do not reach solar; the third is unchanged.
Why “special rate” sounds bad but rarely costs you
Special-rate classification means a slower pool rate (6% vs the main pool) and exclusion from the new 40% main-rate FYA. That sounds like a disadvantage, and at the margin it is — but it almost never bites, because the AIA overrides the pool rate and gives 100% first-year relief on special-rate assets up to £1m. For the overwhelming majority of commercial solar projects, which cost well under £1m, the entire system is relieved at 100% in year one regardless of the special-rate label. The special-rate point only matters above the £1m cap, where the 50% special-rate first-year allowance applies — and even there, it is more generous than the 40% the main-rate allowance would have offered.
So if you have read that the 2026 Budget cut allowances or introduced a 40% allowance and wondered whether to delay a solar project, the answer is no: the solar tax case is essentially unchanged. The full mechanics, worked examples and the above-£1m case are on our capital allowances on solar panels guide.
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